Upright and canister vacuum cleaners equipped with dirt collection assemblies comprising a dirt cup with a tangentially directed inlet and an axially directed outlet are well known in the art. Such a dirt cup provides for cyclonic air flow which utilizes centrifugal force to provide more efficient and effective cleaning of dirt and debris from the air stream.
After a certain period of use the dirt collection chamber in the dirt cup fills with debris and it becomes necessary to empty the dirt cup. Many operators do not enjoy handling the dirt cup and are uncomfortable during the emptying operation. Such operators typically want to minimize any potential contact with the dirt and debris held in the dirt cup. In order to address this concern, it is known in the art to provide a dirt cup with a hinged bottom wall or dump door as disclosed, for example, in U.S. Pat. No. 7,640,624 owned by the Assignee of the present invention. Advantageously, the dump door allows the operator to handle the dirt cup without opening the dirt compartment until the cup is positioned over a garbage can or other receptacle. The dump door is then opened and the dirt and debris in the dirt cup drops under the force of gravity into the underlying garbage receptacle. It should be appreciated that such a dirt cup with a dump door is user friendly, is considered generally more sanitary than other approaches and is a desirable feature.
As noted above, a cyclonic vacuum cleaner utilizes centrifugal force to help separate dirt and debris from the air stream. More specifically, the air stream enters the dirt cup through a tangentially directed inlet and flows rapidly in a cyclonic path around the cylindrical sidewall of the dirt cup. Dirt particles in the air stream move under the resulting centrifugal force produced by this cyclonic movement toward and against the cylindrical sidewall. There the particles slow due to the frictional contact with the sidewall and gradually drop toward the bottom of the dirt cup where they are collected.
It has been found that under certain operating conditions and in certain circumstances the air flow at the bottom of the dirt cup develops an elliptical component. At the same time the air stream typically maintains sufficient velocity to entrain some particles of dirt and debris. Thus, particle backflow may be produced where dirt and debris from the bottom of the cup is lifted back toward the top thereby reducing the overall cleaning efficiency of the vacuum cleaner.
In order to address this concern it is known to reduce turbulence in and particle backflow from the bottom of the dirt cup by positioning vanes or fins on the bottom wall or the outer cylindrical sidewall of the dirt cup as disclosed in, for example, U.S. Pat. Nos. 6,616,721 and 6,810,557. Positioning fins or vanes along the outer sidewall is not the most desirable solution since these vanes are in the path of particle concentration. As a result, the air stream and entrained particles impact the vanes with a high force. Often that force is sufficient to cause substantial airflow turbulence and particle scatter toward the center of the dirt cup where some of the particles have a tendency to be lifted toward the airstream outlet leading from the dirt collection chamber. This can adversely affect the cleaning efficiency of the vacuum cleaner.
While the positioning of the vanes or fins in the dirt cup along the bottom wall but spaced from the sidewall avoids this problem, such vanes are not compatible with a dirt cup with a hinged bottom wall or dump door. This is because these vanes would engage the sidewall of the dirt cup and prevent the bottom wall/dump door from opening completely thereby interfering with the dirt dumping or cup emptying operation.
The present invention relates to a vacuum cleaner incorporating a novel dirt collection assembly equipped with both a dump door and fins or vanes to reduce turbulence and particle back flow so as to allow more efficient cleaning operation. Thus, the present invention relates to the first floor cleaning apparatus to both incorporate and benefit fully from these two, previously incompatible features.